io_arm_poll_handler
if (io_arm_poll_handler(req, issue_flags) != IO_APOLL_OK)
if (io_arm_poll_handler(req, issue_flags) == IO_APOLL_OK)
switch (io_arm_poll_handler(req, 0)) {
int io_arm_poll_handler(struct io_kiocb *req, unsigned issue_flags);